The Missile Defense Agency (MDA) is tasked to develop an integrated, layered Ballistic Missile Defense System (BMDS) to defend the United States, its deployed forces, allies, and friends from ballistic missile attack. The MDA BMDS strategy covers all phases of target ballistic missile flight, including boost, midcourse, and terminal. The current Aegis BMD supports the MDA goal by providing hit-to-kill interceptor missile engagement capability against target ballistic missiles in the midcourse phase. Fielded capability of the current Aegis BMD does not launch against or intercept target missiles while in their boost phase.
When launching an interceptor missile, such as the four-stage Standard Missile 3 (SM-3) from an Aegis firing ship against a hostile missile, the first stage is launched in the direction of the predicted intercept point of the target missile. The second stage is guided using midcourse guidance to a waypoint, which defines the end of the second stage of guidance, and is consistent with an updated predicted intercept point calculated by the Aegis Weapon System (AWS), assuming a ballistic target trajectory (target missile is under the influence of only gravitational forces). The third stage is guided to the updated predicted intercept point using inertial guidance performed by the interceptor missile. Terminal guidance of the SM-3 interceptor missile is performed by the fourth stage kinetic warhead using a modified version of proportional navigation to effect a hit-to-kill intercept of the target missile.
The current second-stage midcourse guidance may not be fully effective against a boosting target missile, and improved midcourse guidance is desired which is generalized in the sense that engagements of both boosting and ballistic target missiles are facilitated.